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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"
  1. GRB 210930A: CAHA 2.2m telescope optical limit
  2. GRB 210927A: GIT optical follow-up of ZTF21acdwctm.
  3. Fermi trigger No 654739449: Global MASTER-Net observations report
  4. Swift GRB211001.03: Global MASTER-Net observations report
  5. Swift Trigger 1076121 is not a GRB
  6. Swift GRB211001.03: Global MASTER-Net OT detection
  7. GRB 210930A: Swift/UVOT Upper Limits
  8. GRB 210930A: Swift-XRT refined Analysis
  9. Swift GRB 210930A: Global MASTER-Net observations report
  10. GRB 210930A: Enhanced Swift-XRT position
  11. Fermi trigger No 654658271: Global MASTER-Net observations report
  12. Fermi GRB 210929B: Global MASTER-Net observations report
  13. GRB 210930A: Swift detection of a burst
  14. GRB 210929B: Fermi GBM Final Real-time Localization
  15. Fermi-LAT Gamma-ray Observations of IceCubeCascade-210926A
  16. GRB 210929A: Fermi GBM Final Real-time Localization
  17. GRB 210927A: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 654396242)
  18. GRB 210925B: AstroSat CZTI detection
  19. IceCube-210922A: SMA observation for the JCMT candidate
  20. IPN triangulation of GRB 210925B
  21. GRB 210926A: AstroSat CZTI detection
  22. GRB 210919A: iTelescope T-11 upper limits
  23. IceCube-210926A: No neutrino counterpart candidates in ANTARES search
  24. GRB 210926A: GECAM detection
  25. GRB 210927A: Fermi GBM Final Real-time Localization
  26. GRB 210919A OSN 1.5m Source Confirmation
  27. GRB 210919A CAHA 2.2m Observations: Afterglow/Host Galaxy Candidate
  28. IceCube-210922A: JCMT/SCUBA2 observations
  29. GRB 210925A: GECAM detection
  30. GRB 210925A: Fermi GBM Final Real-time Localization
  31. GRB 210919A: Chandra rapid ToO upper limit
  32. GRB 210924A: Fermi GBM Final Real-time Localization
  33. IceCube-210922A: No Candidate Counterparts from Swift/XRT follow up observations
  34. IceCube-210922A: No significant detection in HAWC
  35. IceCube-210922A: No neutrino counterpart candidates in ANTARES search
  36. GRB 210923B: GECAM detection
  37. Retraction of Fermi GBM GRB 210923A: the trigger is not a GRB
  38. IceCube-210922A: Upper limits from a search for additional neutrino events in IceCube
  39. IceCube-210922A: Upper limits from Fermi-GBM Observations
  40. IceCube-210922A: No Candidate Counterparts from the Zwicky Transient Facility
  41. GECAM observations of a series of bursts from SGR J1935+2154 (2021-09-15T14 to 2021-09-23T14)
  42. GRB 210919A: DECam Upper Limits
  43. Fermi-LAT Gamma-ray Observations of IceCube-210922A
  44. Konus-Wind detection of a burst from SGR 1935+2154 on 2021 September 22
  45. GRB 210923A: Fermi GBM Final Real-time Localization
  46. IceCube Alert 210922.76: Global MASTER-Net observations report
  47. GRB 210919A: Swift-BAT refined analysis
  48. IceCube-210922A - IceCube observation of a high-energy neutrino candidate track-like event
  49. GRB 210912A: LBT optical observations
  50. GRB 210919A: Lowell Discovery Telescope upper limits (correction to GCN 30859)
  51. GRB 210919a: Lowell Discovery Telescope upper limits
  52. GRB210919A: Keck NIRC2 Kp band upper limits
  53. GRB 210919A: Swift/UVOT Upper Limits
  54. GRB 210919A: LOAO and LSGT optical upper limits
  55. GRB 210919A: MITSuME Akeno optical upper limits
  56. GRB 210919A: Swift-XRT refined Analysis
  57. GRB 210919B: Fermi GBM Final Real-time Localization
  58. GRB 210919A: NOT upper limits
  59. GRB 210919A: AbAO optical upper limit
  60. GRB 210919A: Enhanced Swift-XRT position
  61. GRB 210919A: LCO Optical Upper Limit
  62. GRB 210919A: BOOTES-2/TELMA optical upper limit
  63. Swift GRB 210919A: Global MASTER-Net observations report
  64. GRB 210919A: Swift detection of a short burst
  65. Swift trigger 1073821: detection of IGR J16418-4532
  66. GRB 210912A: BOOTES-5/JGT optical afterglow candidate (Correction to GCNC 30823)
  67. GRB 210917A: Fermi GBM Final Real-time Localization
  68. GRB 210812A is not a compelling example of a lensed GRB
  69. GECAM observations of bursts from SGR J1935+2154 (2021-09-13T01 to 2021-09-15T14)
  70. GRB 210909A: Detection by GRBAlpha
  71. GRB 210912A: Swift-BAT refined analysis
  72. Konus-Wind observation of the recent SGR 1935+2154 activity
  73. GRB 210912A: Tautenburg observations
  74. GECAM observations of bursts from SGR J1935+2154 (2021-09-12T05 to 2021-09-13T01)
  75. AGILE observations of two bright bursts from SGR 1935+2154
  76. GRB 210912A: CAHA 2.2m Detection
  77. GRB 210912A: Swift-XRT refined Analysis
  78. GRB 210912A: Swift/UVOT Detection
  79. Fermi GBM observation of another bright burst in the direction of SGR 1935+2154
  80. GRB 210912A: Enhanced Swift-XRT position
  81. GRB 210912A: Host-galaxy candidate in PanSTARRS
  82. Fermi trigger No 653151835: Global MASTER-Net observations report
  83. Fermi trigger No 653124492: Global MASTER-Net observations report
  84. Fermi trigger No 653122278: Global MASTER-Net observations report
  85. GRB 210912A: Mondy optical afterglow confirmation
  86. Swift GRB 210912A: Global MASTER-Net observations report
  87. GRB 210912A: BOOTES-5/JGT optical afterglow candidate
  88. GECAM observations of bursts from SGR J1935+2154 (2021-09-11T07 to 2021-09-12T08)
  89. GRB 210912B: Fermi GBM Final Real-time Localization
  90. GRB 210912A: Swift detection of a burst
  91. Fermi trigger No 653093506: Global MASTER-Net observations report
  92. Fermi trigger No 653066776: Global MASTER-Net observations report
  93. Fermi trigger No 653084584: Global MASTER-Net observations report
  94. Fermi trigger No 653083551: Global MASTER-Net observations report
  95. Fermi trigger No 653079281: Global MASTER-Net observations report
  96. Fermi trigger No 653066130: Global MASTER-Net observations report
  97. Fermi trigger No 653072474: Global MASTER-Net observations report
  98. Fermi trigger No 653071808: Global MASTER-Net observations report
  99. Fermi trigger No 653054042: Global MASTER-Net observations report
  100. Fermi trigger No 653049776: Global MASTER-Net observations report

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